Suicide (Latin suicidium, from sui caedere, "to kill oneself") is the act of intentionally causing one's own death. Suicide is often committed out of despair, the cause of which is frequently attributed to a mental disorder such as depression, bipolar disorder, schizophrenia, alcoholism, or drug abuse.Stress factors such as financial difficulties or troubles with interpersonal relationships often play a role. Efforts to prevent suicide include limiting access to firearms, treating mental illness and drug misuse, and improving economic development.

        从字面的意思可以看出，自杀（suicide）的原因主要分为mental disorder和stress factor，其实stress factor到了一定程度也可以转化为mental disorder，所以自杀主要是mental disorder引起的内在行为。这当然是针对人所下的定义，对于一些动物如猩猩、狗和猫等是否有自杀的行为呢？在现实的生活中，很少见有动物发生自杀行为，是不是动物们的神经系统不够发达？如果将高级动物施加外在压力，是否能够刺激动物自杀的倾向？

        只是不经意间的随便想想，还请博主达人们解惑也~！